Diels-Alder reaction of pyran-2(<i>H</i>)-ones: Part V^†—Diels-Alder reaction of 4,6- disubstituted pyran-2(<i>H</i>)-ones with 1,4-naphthoquinone and <i>N</i>-phenylmaleimide under Dry State Adsorbed Condition (DSAC) on montmorillonite Kl0, filtrol-24, bentonite, pyrophyllite; and Al³⁺, Zn²⁺, Fe³⁺ exchanged montmorillonite K10 and bentonite

Abstract

The Diels-Alder reaction of 4,6-bis( 4-methoxyphenyl)-, and 4-(4-methoxyphenyl)-6-methylpyran-2(<i>H</i>)-ones has been carried out with 1,4-naphthoquinone and <i>N</i>-phenylmaleimide under Dry State Adsorbed Condition (DSAC) on montmorillonite K10, filtrol-24, bentonite and pyrophyllite clays. Pyrophyllite has been found to be the poorest in catalysing the reaction; while filtrol-24 is the best. Montmorillonite and bentonite are impregnated with AlCl₃, ZnCl₂ and FeCl₃ using their aqueous (AA) and nonaqueous (OO) (AlCl₃-nitrobenzene, ZnCl₂ and FeCl₃-acetonitrile) solutions. For the nonaqueous

impregnation after washing with water a new catalyst (OA) is obtained. The Diels-Alder reaction has been carried out under DSAC using these Lewis acids doped clay catalysts. FeCl₃ impregnated (OA) type catalyst is found to be the best.